When I read a subscription on Google Reader, Google just-in-time loads more entries as I reach the bottom of the page. It would be nice to have the SO sites do this too instead of having a pager on questions with lots of answers.

For SO, I actually prefer paging. Other sites like DZone use this auto-scrolling behaviour. I guess to seem more app-like than Web-like but honestly I tend to just find it annoying and unnecessary most of the time.

Paging makes it easy to get to the last page or even to a specific page (not often used but sometimes it is).

I do think it works for Google Reader but you'll note that others like Gmail use traditional paging.